1. Field of the Invention
This invention relates to winches, and, more particularly, to a hand operated, self-locking winch which is relatively silent in operation.
2. Description of the Prior Art
Hand operated winches are used in a wide variety of applications for forcibly retracting a cable, rope or other elongated member. Very often the load at the end of the cable exerts a constant force away from the winch so that the winch crank must be held immobile in order to prevent cable from unwinding from the cable drum. In order to prevent the cable from unwinding from the winch, latching mechanisms are frequently utilized to prevent rotation of the cable drum. These mechanisms generally include a pawl resiliently biased against the teeth of a ratchet wheel mounted on the cable drum. The pawl is lifted from the ratchet wheel in order to allow unwinding of cable from the drum. One surface of the pawl is generally beveled to allow the teeth of the ratchet wheel to move beneath the pawl in one direction while preventing the wheel from rotating in the opposite direction. As cable is wound on the drum, the pawl sequentially climbs over the teeth of the ratchet wheel and, after each tooth has been cleared, forcibly strikes the next adjacent tooth. Thus, as the pawl clears each tooth of the ratchet wheel, a relatively loud noise is produced. In many applications, such as in the construction industry, this noise is not particularly objectionable. However, in other applications, such as in hospitals, office buildings and other environments where it is desirable to keep noise at a minimum, winches using such latching mechanisms are unacceptable.
One of the primary advantages of conventional pawl and ratchet latching mechanisms is that they are both inexpensive and effective. The mechanism includes only three parts -- a ratchet wheel, a pawl and a spring. Furthermore, the strength of the latching mechanism can be adjusted easily simply by scaling up the size of the rattchet and pawl. Thus, except for the noise problem, winches using pawl and latching mechanisms are extremely efficient and inexpensive devices.